What is DNA?DNA- deoxyribonucleic acid, the hereditary material of life in a cell's nucleus | genes- carries codes for traits | trait- characteristic of an organism | acquired trait- from your parents | environmental trait- from the surrounding environment | chromosomes contain genes which are made of DNA | Genes are inherited from your parents. Each gene codes for 1 trait, and thousands of genes are on each chromosome. Chromosomes in humans are arranged into 23 homologous pairs |
DNA StructureDNA is a double helix, and consists of phosphate, deoxyribose sugar, and nitrogen bases. Phosphate and sugar make the backbone, and nitrogen bases are the rungs of the ladder. | nucleotide- a phosphate paired with a nitrogen base and deoxyribose sugar | histone- special proteins that prevent DNA from tangling | nucleosome- DNA and histone packages which resemble beads | telomere- protective end on eukaryotic cells that shortens every time DNA replicates |
The 4 Nitrogen BasesPURINES
(single-ringed) | PYRIMIDINES
(double-ringed) | Adenine to | Thymine with 2 H-bonds | Guanine to | Cytosine with 3 H-bonds |
What Causes Genetic Diversity?1. Crossing over in prophase I | 2. Independent assortment in metaphase I and II. The chromosomes line up randomly each time. |
Non-Disjunctionnon-disjunction- a mistake that occurs during anaphase I and II, when the chromosomes do not separate and gametes end up having the wrong number |
Mitosis vs MeiosisMITOSIS | BOTH | MEIOSIS | - all daughter cells are somatic | - both for the purpose of reproduction | - all daughter cells are gametes | - 2 similar cells are produced | - both create daughter cells | - 4 different cells are produced | - 46 chromosomes | | - 23 chromosomes | - DNA is not crossed over | | - DNA is crossed over |
Meiosis I and Meiosis IIMEIOSIS I | MEIOSIS II | Prophase I
centrioles move to opposite poles, homologous chromosomes become visible and form tetrads, crossing over occurs, genetic material is exchanged | Prophase II
- centrioles move to opposite poles, chromosome pairs become visible, crossing over does NOT occur | Metaphase I
- tetrads line up along the equator of the cell (staying as a pair) | Metaphase II
- each chromosome moves to the equator of the cell | Anaphase I
- homologous chromosomes are pulled apart creating whole paired chromosomes on each side | Anaphase II
- each chromosome splits and moves to opposite poles, the chromatid is now considered the chromosome | Telophase I
- nuclear membrane reforms, cytokinesis occurs, creating 2 diploid cells, which contain 46 chromosomes and are genetically different | Telophase II
- nuclear membrane reforms, cytokinesis occurs, creating 4 haploid cells called gametes |
| | Prokaryotes vs EukaryotesPROKARYOTES | BOTH | EUKARYOTES | - no nucleus or organelles | - both forms of life | - nucleus and organelles | - simple and primitive | | - complex cells | - usually single-celled | | - can be multicellular |
Meiosis Definitionszygote- cell created when egg and sperm unite | karyotype- map of chromosomes organized into homologous pairs | diploid- total # of chromosomes in an organism, somatic cells | haploid- half the # of chromosomes in an organism, sex cells |
Purpose of Mitosis and MeiosisMITOSIS | MEIOSIS | 1. Asexual Reproduction
- 1 parent with identical offspring | 1. Create Gametes
- creates egg/sperm or egg/pollen
- 2 parents with genetically different offspring | 2. Repair
- to fix damaged cells and replace old cells | 3. Growth
- nuclear division, and depends
on the size and growth of the
organism |
Mutationmutation- any change made to DNA |
4 Types of Mutations1. Translocation | - part of a chromosome breaks off and attaches itself to a different chromosome
- Translocation Down's | 2. Deletion | - part of a chromosome is deleted
- Prader Willi Syndromelearning disabilities, behavioural problems, obesity, short stature, etc. | 3. Duplication | - part of the chromosome is repeated
- cause of seizures | 4. Inversion | - genetic code is flipped
- linked to infertility problems |
Trisomies and TraitsTrisomy 13, Patau Syndrome | heart defects, brain and spinal cord abnormalities, extra fingers and toes, cleft lip, usu. die by 1 yr. old | Trisomy 18, Edward Syndrome | abnormally shaped head, clenched fists, heart defects, usu. die by 1 yr. old | Trisomy 21, Down Syndrome | mild disability, can still form relationships and interact in society | Trisomy XXY, Klinefelter Syndrome | infertile males, look childish, high pitched voice, learning disabilities |
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